Inorganic-organic synthetic materials based on polyisocyanates and aqueous alkali metal silicate solutions are already known and are described, for example, in German Offenlegungsschrift No. 1,770,384; U.S. application Ser. No. 527,476, now U.S. Pat. No. 4,097,423; U.S. application Ser. No. 527,478, filed Nov. 26, 1974, now abandoned and U.S. Pat. Nos. 3,965,051, 3,981,831, 3,985,929, 4,042,536 and 4,052,347.
It is possible in this way to produce synthetic materials which, because of their inorganic content, are more fire-resistant than purely organic materials. They may be cellular or non-cellular, hard or soft, brittle or flexible, depending on their composition and the reaction conditions under which they have been produced. These inorganic-organic synthetic materials are suitable for a wide variety of uses due to the great variation in their properties.
Common to all of these materials is that to produce them, the inorganic and organic phases must be mixed together. W/O type dispersions (water-in-oil) or O/W type dispersions (oil-in-water) are thereby obtained. The synthetic materials which are obtained from a W/O type dispersion are particularly interesting. They have great mechanical strength, even when exposed to moisture, because the hardened continuous organic phase envelops the hardened aqueous inorganic discontinuous phase and thereby fixes it. The improved fire resistance of such systems also depends on the perfectly continuous organic phase of these materials due to the water which is enclosed by this phase.
Attempts have been made to produce the synthetic materials described above by mixing the starting components in an intermittently or continuously operating mixing apparatus in one or more stages and then leaving the resulting dispersion to solidify.
However, the products obtained by this method generally lose their mechanical strength progressively with the increasing proportion of inorganic component in them, and in extreme cases they may even disintegrate to a sandy texture and have cavities. However, it is precisely these products with a large inorganic content which are particularly interesting in economic grounds and because of their greater fire resistance.
It is an object of the present invention to obviate the disadvantages described above and to provide a problem-free method of producing inorganic-organic synthetic materials with even large quantities of inorganic components.
These problems are solved by the process according to the invention.